i hear good things about plants that use both all the way through...15w isnt nearly enough though...the 400w hps is probally plenty ucould prob grow 5 plants under that thing...

usually people use cfls during veg and hps/mh during flower

just keep in mind thats tempuatre control is very important and a 400w hps in a small cabinet will need good ventilation, stick a fan in there or soemthing and u should be fine